(153591) 2001 SN₂₆₃

(153591) 2001 SN263
Discovery
Discovered by	LINEAR
Discovery date	20 September 2001
Designations
Minor planet category	Amor asteroid, NEO
Orbital characteristics
	Epoch 13 January 2016 (JD 2457400.5)
	Uncertainty parameter 0
Observation arc	9198 days (25.18 yr)
Aphelion	2.93738213 AU (439.426112 Gm)
Perihelion	1.03628119 AU (155.025459 Gm)
Semi-major axis	1.98683166 AU (297.225786 Gm)
Eccentricity	0.47842527
Orbital period (sidereal)	2.80 yr (1022.9 d)
Mean anomaly	297.359818°
Mean motion	0° 21m 6.966s / day
Inclination	6.6857915°
Longitude of ascending node	325.831561°
Argument of perihelion	172.862511°
Earth MOID	0.0504696 AU (7.55014 Gm)
Jupiter MOID	2.11282 AU (316.073 Gm)
Physical characteristics
Dimensions	2.8 km
Mean radius	1 km
Mass	~1.5×1013 kg
Mean density	1.3±0.6 g/cm³
Equatorial surface gravity	0.045 cm/s²
Equatorial escape velocity	110 cm/s
Synodic rotation period	3.423 h (0.1426 d)
Geometric albedo	0.05
Spectral type	C-complex
Absolute magnitude (H)	16.9

(153591) 2001 SN₂₆₃ is a small near-Earth asteroid discovered by the LINEAR project in 2001. In 2008, scientists using the planetary radar at Arecibo Observatory discovered that the object is orbited by two satellites, when the triple asteroid made a close approach to Earth of 0.066 AU (nearly 10 million kilometers). The largest body is called Alpha and is spheroid in shape, with principal axes of 2.8±.1 km, 2.7±.1 km, and 2.5±.2 km and a density of nearly 1.3±0.6 g cm⁻³,^[2] and the satellites, named Beta and Gamma, are several times smaller in size. Beta is 1.1 km in diameter and Gamma 0.4 km.

The only other unambiguously identified triple asteroid in the near-Earth population is (136617) 1994 CC, which was discovered to be a triple system in 2009.

Orbital characteristics of satellites

The orbital properties of the satellites are listed in this table.^[3] The orbital planes of both satellites are inclined relative to each other; the relative inclination is about 14 degrees. Such a large inclination is suggestive of past evolutionary events (e.g. close encounter with a terrestrial planet, mean-motion-resonance crossing) that may have excited their orbits from a coplanar configuration to an inclined state.

Name	Mass [kg]	Semi-major axis [km]	Orbital period [days]	Eccentricity
Gamma (inner)	~10×10¹⁰	3.8	0.686	0.016
Beta (outer)	~24×10¹⁰	16.6	6.225	0.015

References

^ ^a ^b "153591 (2001 SN263)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 7 April 2016.
^ http://adsabs.harvard.edu/abs/2008DPS....40.2806B Physical Modeling of Triple Near-Earth Asteroid 153591 (2001 SN263)
^ Fang, Julia. "Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution". Astronomical Journal. 141: 154. arXiv:1012.2154. Bibcode:2011AJ....141..154F. doi:10.1088/0004-6256/141/5/154. Retrieved 8 November 2012.

External links

(153591) 2001 SN263 at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters
Robert Roy Britt, Triple Asteroid Found Near Earth, Space.com, 13 Feb 2008
Emily Lakdawalla, Triple Near-Earth Asteroid Discovered The Planetary Society, 13 Feb 2008
Images of the asteroid and its moons
Julia Fang, "Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution", [1]
A Lander to Investigate a C-type Triple Near-Earth Asteroid System: 2001 SN263
[2]

[jpldata-1] "153591 (2001 SN263)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 7 April 2016.

[2] ttp://adsabs.harvard.edu/abs/2008DPS....40.2806B Physical Modeling of Triple Near-Earth Asteroid 153591 (2001 SN263)

[Fang11-3] Fang, Julia. "Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution". Astronomical Journal. 141: 154. arXiv:1012.2154. Bibcode:2011AJ....141..154F. doi:10.1088/0004-6256/141/5/154. Retrieved 8 November 2012.

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